How can add overlay to map on android?

问题

i tried to apply these codes that is in this link. But I'm getting error like NullPointerException.

I use fragmentation and here is my function that is in my BaseFragment

 public void createMapViewForHaritaFragment(IlanList list)
{
    IlanList gelenListe;
    gelenListe=list;

    if(gelenListe!=null)
    {
        MainActivity parent = getParentActivity();
        mMapViewContainer = parent.getmMapViewContainer();
        mMapView = parent.getmMapView();

        /**/
            mc = mMapView.getController();

            LocationManager lm = (LocationManager) parent.getSystemService(parent.getApplicationContext().LOCATION_SERVICE); 
            Location location = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
            String longitude = String.valueOf(location.getLongitude()).substring(0, 9);
            String latitude = String.valueOf(location.getLatitude()).substring(0, 9);


            String coordinates[] = {latitude,longitude};
            double lat = Double.parseDouble(coordinates[0]);
            double lng = Double.parseDouble(coordinates[1]);

            p = new GeoPoint(
                (int) (lat * 1E6), 
                (int) (lng * 1E6));

            mc.animateTo(p);
            mMapView.setBuiltInZoomControls(true);      

            mMapView.setSatellite(false);               
            mc.setZoom(16);         




            /*Harita
            public View mMapViewContainer;
            public MapView mMapView;
            public MapController mc;
            public GeoPoint p;

            public List<Overlay> mapOverlays;
            public Drawable drawable;
            public MapItemizedOverlay itemizedOverlay;  
            Harita*/

            drawable = this.getResources().getDrawable(R.drawable.map_kirmizi_png);
            itemizedOverlay = new MapItemizedOverlay(drawable, parent.getApplicationContext(), 30);//text size: 30

            GeoPoint gPointMe = new GeoPoint(41099932,29002657);
            OverlayItem overlayItem = new OverlayItem(gPointMe, "Me", "This is my location");
            itemizedOverlay.addOverlay(overlayItem);    

            mapOverlays.add(itemizedOverlay);

            mMapView.setBuiltInZoomControls(true);

            //move map over to my position
            mc.animateTo(gPointMe);  



        mMapView.invalidate();
    }

}

And I think, I'm getting error while processing this code :

protected OverlayItem createItem(int i)
{
    return mOverlays.get(i);
}

These are my LogCat.

12-21 12:35:53.443: E/AndroidRuntime(19782): FATAL EXCEPTION: main
12-21 12:35:53.443: E/AndroidRuntime(19782): java.lang.NullPointerException
12-21 12:35:53.443: E/AndroidRuntime(19782):    at com.mert.fragment.BaseFragment.createMapViewForHaritaFragment(BaseFragment.java:274)
12-21 12:35:53.443: E/AndroidRuntime(19782):    at com.mert.fragment.impl.EtrafimdaHaritaFragment$MyHandler.handleMessage(EtrafimdaHaritaFragment.java:154)
12-21 12:35:53.443: E/AndroidRuntime(19782):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-21 12:35:53.443: E/AndroidRuntime(19782):    at android.os.Looper.loop(Looper.java:143)
12-21 12:35:53.443: E/AndroidRuntime(19782):    at android.app.ActivityThread.main(ActivityThread.java:4277)
12-21 12:35:53.443: E/AndroidRuntime(19782):    at java.lang.reflect.Method.invokeNative(Native Method)
12-21 12:35:53.443: E/AndroidRuntime(19782):    at java.lang.reflect.Method.invoke(Method.java:507)
12-21 12:35:53.443: E/AndroidRuntime(19782):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-21 12:35:53.443: E/AndroidRuntime(19782):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-21 12:35:53.443: E/AndroidRuntime(19782):    at dalvik.system.NativeStart.main(Native Method)

Thanks for your help.

回答1:

        AddItemized Overlay class:

        public class AddItemizedOverlay extends ItemizedOverlay<OverlayItem> {

            private ArrayList<OverlayItem> mapOverlays = new ArrayList<OverlayItem>();

            private Context context;

            public AddItemizedOverlay(Drawable defaultMarker) {
                 super(boundCenterBottom(defaultMarker));
            }

            public AddItemizedOverlay(Drawable defaultMarker, Context context) {
                 this(defaultMarker);
                 this.context = context;
            }

            @Override
            protected OverlayItem createItem(int i) {
               return mapOverlays.get(i);
            }

            @Override
            public int size() {
               return mapOverlays.size();
            }

            @Override
            protected boolean onTap(int index) {
               Log.e("Tap", "Tap Performed");
               return true;
            }

            public void addOverlay(OverlayItem overlay) {
               mapOverlays.add(overlay);
                this.populate();
            }

         }


    Use this code in your Activity


      List<Overlay> mapOverlays = mv.getOverlays();
            Drawable drawable = this.getResources().getDrawable(R.drawable.drawable);
            AddItemizedOverlay itemizedOverlay =
            new AddItemizedOverlay(drawable, this);
            OverlayItem overlayitem = new OverlayItem(gp, "Hello", "I am here");
            itemizedOverlay.addOverlay(overlayitem);
            mapOverlays.add(itemizedOverlay);


 public void createMapViewForHaritaFragment(IlanList list)
{
    IlanList gelenListe;
    gelenListe=list;

    if(gelenListe!=null)
    {
        MainActivity parent = getParentActivity();
        mMapViewContainer = parent.getmMapViewContainer();
        mMapView = parent.getmMapView();

        /**/
            mc = mMapView.getController();

            LocationManager lm = (LocationManager) parent.getSystemService(parent.getApplicationContext().LOCATION_SERVICE); 
            Location location = lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
            String longitude = String.valueOf(location.getLongitude()).substring(0, 9);
            String latitude = String.valueOf(location.getLatitude()).substring(0, 9);


            String coordinates[] = {latitude,longitude};
            double lat = Double.parseDouble(coordinates[0]);
            double lng = Double.parseDouble(coordinates[1]);

            p = new GeoPoint(
                (int) (lat * 1E6), 
                (int) (lng * 1E6));

        mc = mMapView.getController();
        mc.setCenter(p);
        mc.setZoom(16);

        List<Overlay> mapOverlays = mv.getOverlays();
        Drawable drawable = this.getResources().getDrawable(R.drawable.pin);
        AddItemizedOverlay itemizedOverlay = new AddItemizedOverlay(drawable,
                this);
        OverlayItem overlayitem = new OverlayItem(p, "Hello", "I AM HERE");
        itemizedOverlay.addOverlay(overlayitem);
        mapOverlays.add(itemizedOverlay);

           /* mc.animateTo(p);
            mMapView.setBuiltInZoomControls(true);      

           mMapView.setSatellite(false);               
           mc.setZoom(16);   */      




            /*Harita
            public View mMapViewContainer;
            public MapView mMapView;
            public MapController mc;
            public GeoPoint p;

            public List<Overlay> mapOverlays;
            public Drawable drawable;
            public MapItemizedOverlay itemizedOverlay;  
            Harita*/

          /*  drawable = this.getResources().getDrawable(R.drawable.map_kirmizi_png);
            itemizedOverlay = new MapItemizedOverlay(drawable, parent.getApplicationContext(), 30);//text size: 30

            GeoPoint gPointMe = new GeoPoint(41099932,29002657);
            OverlayItem overlayItem = new OverlayItem(gPointMe, "Me", "This is my location");
            itemizedOverlay.addOverlay(overlayItem);    

            mapOverlays.add(itemizedOverlay);

            mMapView.setBuiltInZoomControls(true);

            //move map over to my position
            mc.animateTo(gPointMe);  



        mMapView.invalidate(); */
    }

}

来源：https://stackoverflow.com/questions/13988744/how-can-add-overlay-to-map-on-android